CODEWITHSUNDEEP
pythonpython-3.xcaesar-cipher
808Blues
808Blues

Reputation: 83

Caesar Cipher python with alphabet input

I'm a beginner in python and taking a course on it. I've been tasked with making a caesar cipher where I can input the alphabet used. For this I can't use ord() or list() or any imported functions, only basic python. I've got it to work for one letter but I can't seem to figure out how to make it work for more than one letter. Any help would be greatly appreciated!

def cypher(target, alphabet, shift):
    
    for index in range( len(alphabet)):
        if alphabet[index] == target:
           x = index + shift
           y =  x % len(alphabet)
                  
    return (alphabet[y])

Upvotes: 2

Views: 3829

Answers (2)

ti7
ti7

Reputation: 18826

There are many ways to accomplish such a thing, but you probably want a form of

  • get the input values
  • construct your mapping and store it (perhaps in a dictionary at first for some sort of per-value comparison or directly as a str.maketrans table)
  • take a look to see that it's what you want and expect
  • perform the cipher operation
  • give back the results (showing the original string on the line above or below the result can help spot issues!)

Here's a complete example for a very boring Caesar Cipher

source_string = input("source string: ").upper()
cut_position  = int(input("rotations: "))

# available as string.ascii_uppercase
source_values = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

# create a mapping
mapping = source_values[cut_position:] + source_values[:cut_position]

# display mapping
print("using mapping: {}".format(mapping))

# build a translation table
table = str.maketrans(source_values, mapping)

# use your translation table to rebuild the string
resulting_string = source_string.translate(table)

# display output
print(resulting_string)

Providing a mapping and lowercasing text is left as an exercise

Upvotes: 0

Suraj Upadhyay
Suraj Upadhyay

Reputation: 475

I see this is your first question. Thanks for asking.

I think what you want your code to encrypt a full length script using the function you built above. So, what your function does is it takes a letter as target and shifts it.

This can easily be applied to a string by iterating over its elements.

I have provided the correct implementation for your query with some tweaks here :

alphabet = "abcdefghijklmnopqrstuvwxyz"

def cypher(target, shift):
    for index in range(len(alphabet)):
        if alphabet[index] == target:
            x = index + shift
            y =  x % len(alphabet)
            return (alphabet[y])


string = "i am joe biden"
shift = 3 # Suppose we want to shift it for 3
encrypted_string = ''
for x in string:
    if x == ' ':
        encrypted_string += ' '
    else:
        encrypted_string += cypher(x, shift)

print(encrypted_string)

shift = -shift # Reverse the cypher
decrypted_string = ''
for x in encrypted_string:
    if x == ' ':
        decrypted_string += ' '
    else:
        decrypted_string += cypher(x, shift)

print(decrypted_string)

Upvotes: 0

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